Pathogenic waste treatment

Abstract

Solid waste such as sewage sludge containing fecal matter is processed to reduce pathogens by at least 90% and converted to a useful product such as an amendment to agricultural land by combining the waste with an acid such as concentrated sulfuric and a base such as fly ash which exothermically react and thermally pasteurize the waste and add mineral value to the product. Pozzolanic materials, such as fly ash agglomerate the product and after grinding, the particles can aerate soil. The calcium oxide in fly ash reacts with sulfuric acid to form calcium sulfate dihydrate, a soil amendment. The amount of sulfuric acid can be controlled to provide a product with acid pH which is useful to neutralize alkaline soils such as those found in the Western United States of America.

We claim: 
     
       1. A method of disinfecting pathogen-containing solid waste selected from the group consisting of sewage sludge, septage, manure and water treatment plant residuals comprising the steps of: combining the waste with a strong acid having a concentration of at least 25% by weight and with a strong base in an insulated reaction vessel to form a reaction mixture having a pH below 7; and   exothermically reacting the acid with the base in said vessel in the presence of the waste to heat said reaction mixture to a temperature of at least 70 degrees Celsius for at least 30 minutes and reacting said waste with said acid and said base to disinfect at least 90 percent of said pathogens and form a reaction product having a pH below 7 comprising the residue of said disinfected waste and the salt of said acid and said base.   
     
     
       2. A method according to claim 1 in which the acid is selected from the group consisting of sulfuric acid, phosphoric acid, nitric acid, hydrochloric acid, acetic acid or precursors thereof. 
     
     
       3. A method according to claim 2 in which the base is selected from the group consisting of Group I metal, Group II metal, ammonium hydroxides or oxide precursors thereof. 
     
     
       4. A method according to claim 3 in which the base is selected from the group consisting of sodium hydroxide, potassium hydroxide, calcium hydroxide, magnesium hydroxide, calcium oxide, magnesium oxide or ammonium hydroxide. 
     
     
       5. A method according to claim 4 in which the reaction mixture further contains a binder material. 
     
     
       6. A method according to claim 5 in which the binder is a pozzolanic material. 
     
     
       7. A method according to claim 6 in which the pozzolanic material contains said base and is selected from the group consisting of fly ash, kiln dust and cement klinker. 
     
     
       8. A method according to claim 7 in which the pozzolanic material agglomerates the reaction product into a friable mass. 
     
     
       9. A method according to claim 8 further including the step of grinding the friable mass into particles. 
     
     
       10. A method according to claim 4 in which the acid or base is encapsulated in a manner to slowly release from the encapsulant. 
     
     
       11. A method according to claim 10 in which the encapsulant is an aluminasilicate material. 
     
     
       12. A method according to claim 1 in which the reaction mixture further includes a chemical disinfectant. 
     
     
       13. A method according to claim 12 in which the chemical disinfectant is a compound that is generated in situ in the reaction mixture to generate a sterilant gas. 
     
     
       14. A method according to claim 13 in which the sterilant gas is sulfur dioxide. 
     
     
       15. A method according to claim 14 in which the sterilant gas is generated by the acidification of a metal sulfite. 
     
     
       16. A method according to claim 15 in which the acid is sulfuric acid and the base is calcium sulfite. 
     
     
       17. A method according to claim 1 in which the reaction mixtures further includes heavy metal binding agents. 
     
     
       18. A method according to claim 17 in which the metal binding agents are phosphates. 
     
     
       19. A method according to claim 1 in which the reaction mixture contains sufficient nitrogen, potassium, or phosphorous such that the reaction product is useful to be added to land in pasture or agricultural production. 
     
     
       20. A method according to claim 1 in which the solid waste has a solids content from 3 to 85% by weight. 
     
     
       21. A method according to claim 20 in which the waste is present in the reaction mixture in an amount from about 10 to about 40% by weight. 
     
     
       22. A method according to claim 21 in which the acid is present in an amount from about 5 to 25% by weight. 
     
     
       23. A method according to claim 22 in which the base is present in an amount from about 10 to about 40% by weight. 
     
     
       24. A method according to claim 23 in which the acid and base are present in an amount within ±5 to 10% neutralization. 
     
     
       25. A method according to claim 24 in which the acid base pair has a ΔT of at least 50 degrees Celsius. 
     
     
       26. A method according to claim 1 in which the solid waste is sewage sludge, the acid is concentrated sulfuric acid and the base is unquenched fly ash. 
     
     
       27. A method according to claim 26 in which the salt contained in the reaction product is calcium sulfate. 
     
     
       28. A method according to claim 1 in which the solid waste and acid are combined before adding the base. 
     
     
       29. A method according to claim 1 in which the pH of the reaction product is from about 1.0 to about 6.5.